Generally speaking, a sleeve employed as an injection mould is used to seal a leak in fluid pipes. The portion to be repaired is encased by the sleeve, which forms a watertight cavity in which a polymerizable liquid material is injected. As it polymerizes, this liquid forms a coating that seals leaks and provides insulation against heat, chemicals and shocks.
Sleeves that can be used in this technique are described, for example, in the following patents: FR 2.158.895, EP 278.050, U.S. Pat. No. 4,610,740, or GB 2.119.884. They are made up of two cylindrical half-shells joined together to form a single shell covering the portion to be protected or repaired. The polymerizable liquid material (generally made of components of an epoxy resin or polyurethane resin) is then poured through an injection hole provided in the wall of the shell, into the cavity thus created.
These sleeves formed by two half-shells are thus adapted for pipes of a given diameter. Sleeves of different diameters must therefore be available to fit the various pipe diameters. This leads to the necessity of having different moulds to be able to manufacture half-shells having diameters adapted to all pipes, and thus results in a very high cost.
An attempt was thus made to use a modular sleeve as described in the patent EP 0.856.117 made up of identical moulds and thus requiring only one mould for manufacturing modules. In this technique, by varying the number of modules making up the sleeve, the latter can be adapted to pipes of different diameters. In addition, each module includes a male and female portion so that the male portion of a module can fit partially or completely into a female portion of the adjoining module. This allows a sleeve consisting of a fixed number of modules to be adapted to pipes whose diameters are between a minimum value and a maximum value. Unfortunately, due to its modular structure, this type of sleeve does not withstand very high pressures of the order of a few dozen bars to which are subjected certain pipes designed to carry fluids over long distances as is the case with petroleum pipelines.
With the aim of carrying out repairs on high-pressure pipelines, the patent U.S. Pat. No. 5,632,307 describes a device that consists of an elastic band in the form of a coil with multiple windings as on a clock spring that is placed around the pipeline at the defective area. In addition to the fact that the corroded area must be plugged, that the rigid band is difficult to install due to the spring effect, and finally that installing it requires a significant embankment under the pipeline to be able to wind the various layers of the coil, such a device cannot be used if the pipeline is oval, if it is highly bent at the defective area or if, additionally, it is necessary to grind the weld beads, if any, at this location so that the device can operate efficiently.